DNA viruses must traverse two main barriers to reach the cellular compartment for transcription and replication, the cell membrane and the nuclear envelope. Both present sites of potential interference by cellular defense mechanisms. We have identified a third site that is apparently similar for DNA viruses of different families. These few nuclear domains contain several interferon-upregulated proteins, and herpesvirus, adenovirus and SV4O are specifically deposited there after nuclear entry and before transcription begins. This deposition is virus DNA-dependent and has led to the hypothesis that a DNA deposition mechanism exists. We propose to first define this DNA deposition mechanism by determining the targeting or binding signals in DNA from several virus families. This will be accomplished by identifying the location of expression vectors relative to specific nuclear domains, i.e., vectors that contain overlapping viral genome fragments. Secondly, we will determine the functional significance of virus genome deposition at the specific nuclear domain by quantitative assays that determine the transcriptional capacity of specifically targeted and untargeted genes. The potential for targeting genes to nuclear areas of high transcriptional rates could become important for gene therapy.